1. Technical Field
The invention relates generally to a method and apparatus for guiding atoms by blue-detuned evanescent waves in a hollow-core optical fiber. More particularly, the invention relates to the use of a metal-coated hollow-core optical fiber as the wave guide to maximize the evanescent guiding field in the hollow region of the fiber.
2. Background Art
The polarizability of an atom is almost always positive, but it can be negative and some unusual effects can then be observed. This can occur when a laser or other monochromatic source is tuned slightly above or to the "blue" of an atomic resonance. The interaction of the external field on the atom through its negative polarizability produces a gradient dipole force which tends to drive the atom to regions of minimum intensity. Cook and Hill suggested using an evanescent wave to produce an atom mirror outside of a dielectric. Reference: R. J. Cook, R. K. Hill, An Electromagnetic Mirror for Neutral Atoms, Optics Comm. 43 (1982) 258. Zoller, et. al. analyzed the case for a clad, hollow fiber in which the external field was confined to the annular region and used the resulting evanescent field in the hollow region to guide atoms. Reference: S. Marksteiner, C. M. Savage, P. Zoller, S. L. Rolston, Coherent Atomic Waveguides from Hollow Optical Fibers: Quantized Atomic Motion, Phys. Rev. A 50 (1994) 2680. In what has become known as "blue-guiding", Renn and Ito have experimentally demonstrated evanescent wave guiding of rubidium atoms in hollow optical fibers. See: M. J. Renn, E. A. Donley, E. A. Cornell, C. E. Wiemann, D. Z. Anderson, Evanscent-wave Guiding of Atoms in Hollow Optical Fibers, Phys. Rev. A 53 (1996) 648A; and H. Ito, T. Nakata, K. Sakaki, M. Ohtsu, K. I. Lee, W. Jhe, Laser Spectroscopy of Atoms Guided by Evanscent Waves in Micron-sized Hollow Optical Fibers, Phys. Rev. Lett. 76 (1996) 4500.